The present invention relates to a motor vehicle including a preventive protective system.
It is known to equip motor vehicles, such as passenger cars, with active and passive safety devices which allow the driver to better control his vehicle even in critical situations and thus prevent the vehicle from being involved in an accident. Safety devices of this type also contribute to reducing the severity of an accident in the event of a collision.
Safety systems which take preventive action even before a possible collision and use a so-called pre-crash phase (i.e., a period of time starting from when corresponding detection systems in the vehicle detect a high probability of collision until the actual impact) to increase occupant protection by additional safety measures and thus reduce the severity of an accident, are known as preventive protective systems or so-called PRE-SAFE™ systems. Preventive protective systems use information which is provided by various sensor devices of the motor vehicle to identify possible accident situations. The sensor devices are, in particular, a constituent part of an electronic driving stabilizing program and/or a constituent part of a distance sensor system. Conclusions are then drawn about a possible accident on the basis of the identified situation, and corresponding measures for conditioning the vehicle, restraint systems for occupants and possibly protective devices for other involved parties (e.g., pedestrians) for the imminent accident are initiated.
German patent document DE 101 21 386 C1 discloses a method for actuating a reversible occupant protection means in a motor vehicle. The motor vehicle has a reversible occupant protection system which can be activated and thus moved to the active position before a collision occurs. To this end, a sensor system detects driving state data which is monitored for emergency braking, oversteering or understeering operations. If emergency braking, oversteering and/or understeering are/is identified, the occupant protection system is activated, but only when a minimum speed is exceeded. The sensor system for detecting the driving state data may include a steering angle sensor, a pedal travel sensor, a brake pressure sensor, a wheel rotational speed sensor, an acceleration sensor and a yaw rate sensor.
German patent document DE 100 05 010 C2 discloses a method for restraining an occupant on a vehicle seat, with the occupant being drawn into the vehicle seat with a specific force by a reversible belt pretensioner when a critical driving state is identified, and then being held in a drawn-back position on the vehicle seat with a retaining force, with the retaining force being selected to be lower than the force which is used to draw the occupant back onto the vehicle seat, and the retaining force lasting during the identified critical state.
Furthermore, German patent document DE 22 49 759 C2 describes a restraint system for motor vehicle occupants, with a safety belt being tightened starting from a predefined acceleration threshold and the magnitude of the tightening force being set as a function of the change in traveling speed per unit time and/or of the weight of the occupant.
The two solutions known from German patent documents DE 22 49 759 C2 and DE 100 05 010 C2 share the common feature that the force of the respective safety device, i.e., the magnitude of the tightening force of the safety belt, is set as a function of the specified critical driving state and further parameters, it being necessary to avoid excessively high loads on the occupant when pretensioning the belt.
Even if it is possible to use such protective systems, which are also used in practice to set an absolute value that is matched to the safety-critical driving situation, for a force which is to be exerted on the vehicle occupant by the safety device in question, the triggering characteristics of safety belts are primarily designed for the worst-case accident. Thus, although it is possible to vary the belt pretensioning forces of safety belts such that the restraining force is reduced after the belts are triggered, the usually reversible occupant protection means are actuated so quickly that the entire protective action is achieved in the event of the worst-case load situation.
However, triggering characteristics such as these are not required in many critical driving states and in a few critical driving situations have a significant adverse effect on feelings of comfort and acceptance by the vehicle occupants on account of their aggressiveness.
An object of the invention is to provide a motor vehicle including a preventive protective system, which permits a triggering behavior of safety devices which is better matched to the current driving state.
To achieve the above-mentioned object, the invention provides a preventive protective system in a motor vehicle, in which a data evaluation and control device compares the information recorded by a safety sensor system with at least one triggering threshold value and actuates at least one safety device associated with the driving state when a criticality of the driving state is identified. At least triggering of the associated safety devices is actuated with respect to a force/time gradient as a function of the identified criticality of the driving state. This system has the advantage that not only the maximum magnitude of actuating forces of a safety device, but also the actuating forces and actuating times, can be varied and adapted to the existing driving situation.
A criticality of the driving state is usually identified on the basis of an evaluation of the data from a driving state sensor system, but may also include data from a device for identifying the vehicle surroundings.
Therefore, for example, in the case of a reversible belt pretensioner as the associated safety device, the belt pretensioning forces and pretensioning times may be parameterized depending on the existing driving state such that when the vehicle skids with a low frictional force, with the occupants not being moved or being moved only to an insignificant extent on account of low forces of mass inertia, the time until the required belt force is reached is set to be relatively long. In a driving situation such as this, the belt secures the occupant slowly with the required force in a manner which is adapted to the situation.
The actuation of the safety device, which is actuated as a function of the existing driving state, according to the present invention, not only increases the safety of the occupants by avoiding an unadapted, excessively aggressive or excessively soft triggering behavior of the safety device but also considerably increases feelings of comfort of the occupants and therefore acceptance of the entire preventive protective system by the occupants.
In this case, an identified criticality of the vehicle state can not only be understood as a driving state which will probably lead to the vehicle being involved in an accident, but also a driving state which is created in a controlled manner by a sporty driving style and in which the actuation of suitable safety devices is appropriate in order to increase the comfort of the vehicle occupants. Therefore, when traveling around a corner, for example, a vehicle occupant can be slightly drawn into the seat and thus supported better on the sides as a result of the variable design of the force/time gradient of a belt pretensioner, with side cushions of a vehicle seat being better loaded and involved in securing the occupant.
A further contribution to increasing the comfort of the vehicle occupants is made when a maximum force of the associated safety device, which force is parameterized as a function of the identified criticality of the driving state, is reduced over a period of time which can be parameterized. In this way, it is possible, for example, to implement gentle release of a belt pretensioner or of a movable cushion element, such as a knee cushion.
In principle, actuation with a variable force/time gradient is suitable, according to the invention, for all safety devices which are provided in a vehicle, with the safety devices being, for example, a reversible belt pretensioner, an electric seat-adjusting device, a restraint cushion, in particular a knee cushion, whose shape, size and/or position can be adjusted, or other vehicle components which can be electrically, hydraulically or pneumatically adjusted with a view to increasing safety.
In this case, actuation can be performed, according to the invention, by an electric motor which is associated with the respective safety device and whose rotational speed can be variably controlled. Therefore, given corresponding expansion of the engine controller in a controller of a reversible occupant protection device, for example, slower revolutions of the electric motor can slow down tightening of the belt webbing or, when another occupant protection device is used, slow down their extension speed.
Assuming that a longitudinal-dynamics criticality generally constitutes a higher risk to vehicle occupants than a lateral-dynamics criticality, it is advantageous when a longitudinal-dynamics criticality of the driving state is assigned a larger force/time gradient than a lateral-dynamics criticality.
A longitudinal-dynamics criticality, with which activation of safety devices is associated, occurs particularly in the case of emergency braking and panic braking, with emergency braking being identified by a high operating speed of a brake pedal or by a predefined driver reaction. In this case, the triggering threshold can be formed approximately on the basis of a braking assistant being switched on.
Likewise, panic braking (a braking operation in which a deceleration request by the driver is considerably higher than the vehicle deceleration) can advantageously be detected on the basis of a driver reaction. In a driving state such as this, it is advantageous if safety devices are triggered, in principle, only in the case of a low coefficient of friction.
Lateral dynamics-critical driving states include, for example, severe oversteer, severe understeer and critical steering movements.
Actuation of the corresponding safety device can be stated even more precisely and matched to the respective situation if the actuation is carried out as a function of determined physiological variables of an occupant. These include, in particular, the size of vehicle occupants and their weight. This data can be determined by a weight detection device and a body size detection device which are connected to the data evaluation and control device. The weight detection device can be formed as an integral unit with a seat occupancy identification device, and the body size detection device can be formed as an integral unit with a seat position sensor system and an optical, head position determination device, for example.
Using devices such as these, some of which are already installed in the motor vehicle as standard equipment, it is also possible to determine the position of an occupant in the vehicle, which information may be used to actuate the safety device in an exemplary embodiment of the invention.
Important input signals for controlling safety devices include the vehicle speed or a gradient of the vehicle speed, with the force/time gradient of the actuation of a safety device being set as a function of the vehicle speed and/or of a gradient of the vehicle speed, in one exemplary embodiment of the present invention.
In this case, specific safety devices may be activated only starting from a specific vehicle speed and the actuators of the safety devices can only be actuated until the vehicle speed reaches a very low value of, for example, 3 km/h.
A further triggering behavior of safety devices, which behavior is matched to the current driving state, can be achieved if the triggering threshold value is adapted as a function of a total vehicle acceleration and a vehicle speed when a lateral dynamics-critical driving situation is identified.
In this case, the triggering thresholds of the preventive protective system can, for example, be applied separately for high coefficients of friction and for low coefficients of friction.
In the case of a high coefficient of friction, for example, the triggering threshold value which is associated with a lateral dynamics-critical driving situation, such as a state of understeer or a state of oversteer, can be reduced. This leads to an increase in the number of times the preventive protective system is activated at high vehicle speeds, and therefore acceptance of the preventive protection system by a user of the motor vehicle may be increased further.
Designing the preventive protective system in this way means it is possible to map the feeling of danger felt by the vehicle user. The vehicle user generally feels safe at low vehicle speeds and low coefficients of friction, with the result that the triggering threshold value can assume a relatively high value. At high vehicle speeds and high coefficients of friction however, the subjective feeling of danger is generally more pronounced, with the result that the triggering threshold value then advantageously assumes a lower value.
In one exemplary embodiment of the invention, the triggering threshold value is dynamically adapted at least substantially continuously, i.e., smoothly.
Starting from a threshold value at a low vehicle speed and a low total vehicle acceleration (i.e., in the case of a low coefficient of friction), it is expedient to reduce the triggering threshold value by up to approximately 50% as the vehicle speed increases and/or as the total vehicle acceleration increases. This ensures that the preventive protective system always responds in a manner which is matched to the driving situation.
The driving state sensor system may include a sensor system of various designs which is equipped, for example, with a steering angle sensor, a pedal travel sensor, a brake pressure sensor, a wheel rotational speed sensor, an acceleration sensor, a yaw rate sensor and/or a distance sensor.
The data evaluation and control device of the preventive protective system may be a data processing device of a driving stabilizing system of the motor vehicle which is often present in any case, particularly in modern motor vehicles. As an alternative, it is of course possible to employ a separate data processing device.
To identify a lateral dynamics-critical driving situation, such as understeer, in which the radius of the desired path prescribed by the steering angle is less than the radius of the path actually traveled by the vehicle, or oversteer, in which the radius of the desired path prescribed by the steering angle is greater than the radius of the path actually traveled, the total vehicle acceleration, which is found by adding the longitudinal vehicle acceleration and the lateral vehicle acceleration and is determined by corresponding acceleration sensors and possibly by a yaw sensor, may be analyzed. If the analysis shows that the triggering threshold value which varies as a function of the coefficient of friction is exceeded, the data evaluation device outputs a collision plausibility, so that the safety devices which interact with the preventive protective system can be activated and conditioned in accordance with the possible accident situation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.